Liver and muscle are key organs in the regulation of whole body insulin stimulated glucose metabolism and defects in these tissues are the most important factors contributing to insulin resistance in patients with type 2 diabetes. In order to gain a better understanding of understanding of how insulin regulates liver and muscle glucose metabolism in vivo as well as to explore the role of increased free fatty acids in the pathogenesis of insulin resistance in these tissues we plan to use state-of-the-art methods including 13C, 31P and 1H nuclear magnetic resonance spectroscopy in conjunction with GC-MS methods to explore insulin stimulated liver and muscle glucose metabolism in awake rats and unique transgenic and knockout mouse models lack a key insulin signaling and target molecules. The specific biochemical questions that will be addressed are: 1) what is the mechanism by which increased plasma FFA concentration decrease insulin stimulated liver and muscle glucose metabolism in the awake rat and what is the rate controlling step in the process 2) what are the roles of IRS-1 and IRS-2 molecules in insulin stimulated liver and muscle glucose metabolism, 3) what is the impact of tissue specific (muscle and fat) insulin receptor and glut4 knock out on insulin stimulated whole body glucose metabolism in the awake mouse. It is anticipated that the results of these studies will shed new light on the roles of IRS-1 and IRS-2 on insulin stimulated liver and muscle glucose disposal and the mechanism by which increased plasma free fatty acids decreased insulin stimulated glucose metabolism. Such results have important implications for understanding the mechanism of insulin resistance in patients with type 2 diabetes and may help identify potential targets for therapy.